Is Partial Cure a Realistic Endpoint for Novel Hepatitis B Therapy

We read with great interest the article by Sonneveld and Janssen discussing the concept of partial cure in chronic hepatitis B.1 Given the difficulty of achieving a functional cure – defined as hepatitis B surface antigen (HBsAg) seroclearance – partial cure has been proposed as HBsAg <100 IU/ml with HBV DNA below the lower limit of quantification (LLOQ) 24 weeks after treatment cessation.2 The rationale for defining partial cure is to facilitate the development of novel antiviral therapies by allowing a pragmatic off-therapy endpoint indicating a favorable outcome when functional cure cannot be achieved.